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Guidewires

0.035-inch (0.89 mm) flexible wires that serve two foundational roles in urology: gaining access through the urethra or ureter to the bladder / renal pelvis, and providing axial support for the coaxial passage of catheters, stents, dilators, and access sheaths over the wire. Standard length 145–150 cm; 0.038-inch variants exist for stiffer support. The Glidewire (Terumo / Boston Scientific) is the canonical hydrophilic access wire; the Amplatz Super Stiff is the canonical working wire.[1][2]

Core Construction​

CoreMechanical profileNotes
Stainless steel (PTFE-coated)High shaft stiffness, plastic-deformation toleranceTraditional access wire; higher friction, less tip flexibility than nitinol[2][3]
Nitinol (Ni-Ti)Pseudo-elastic — returns to shape after deformationSafest tip on bench testing (lowest pierce / buckle force); lowest friction on human-ureter testing; more inert than stainless steel on SEM of bladder explants[2][3][4]
Hydrophilic polymer coatingSlippery when wet — must be kept wetLowest friction; preferred for difficult access[1][5][6]

Four Functional Categories​

1. Standard (access / floppy-tip) wires​

Flexible 3–15 cm distal tip for initial ureteral / urethral access; moderately stiff shaft.

  • Bentson — long 15 cm floppy tip; least tip-deflection force among standard wires.[1]
  • Roadrunner (Cook) — workhorse access wire; one of only two wires that bypassed an impacted stone in 100% of trials at the highest impaction level.[5]
  • Bard PTFE — stiffest flexible tip among standard wires.[1]

Limitation: standard wires fail (0% success) at the highest-impaction stone model — switch to hydrophilic for any difficult access.[5]

2. Hydrophilic wires — the access workhorse​

Slippery polymer coating dramatically reduces friction against urothelium. Preferred for impacted stones, strictures, tortuous ureters, prior iatrogenic injury, and the Freid–Smith Glidewire technique for failed catheterization.

  • Glidewire (Terumo / Boston Scientific RadiFocus) — least force to bypass an impacted stone (0.117 ± 0.02 lb), shortest insertion time, highest surgeon-satisfaction; highest perforation-force margin (~ 4× other wires, p < 0.01).[1][5][6]
  • HiWire (Cook) — nitinol hydrophilic; second-best for impacted-stone bypass (0.130 ± 0.01 lb).[5]
  • NiCore (Bard) — nitinol hydrophilic; the stiff NiCoreS is one of the stiffest hydrophilic shafts.[6]
  • EZ Glider — lowest tip-bending forces alongside Glidewire / Zipwire; roundest tip in the stiff version.[6]
  • Zipwire (Boston Scientific) — stiff version ZipwireS has the stiffest shaft among hydrophilic wires tested.[6]

Comparative success bypassing impacted stones across 13 wires: hydrophilic 70.67% vs hybrid 36.67% vs standard 0% (p < 0.001).[5]

3. Stiff (working) wires​

Maximum axial rigidity for coaxial passage of UAS, dilators, and stents without buckling.

  • Amplatz Super Stiff (Boston Scientific) — the gold standard; buckling force 1.81 ± 0.91 N vs 0.77–0.80 N for hybrid wires (p < 0.001).[1][7]
  • Amplatz Fixed Core (Cook) — similar working-wire profile.

No standardized definition of "stiffness" across 14 wires from 7 manufacturers (Kolvatzis 2022 SR) — labels alone are not comparable.[8]

4. Hybrid wires​

Stiff shaft + hydrophilic tip — engineering compromise.

  • Sensor (Boston Scientific) — shaft buckling 0.80 ± 0.29 N; intermediate between standard and Amplatz Super Stiff.[7]
  • U-Nite (Bard) — highest lubricity (0.09 ± 0.03 N, p < 0.05).[7]

Bypass impacted-stone success 36.67% — between standard (0%) and pure hydrophilic (70.67%).[5]

Reconstructive-Urology and Urogyn Uses​

The reconstructive-urology applications of guidewires extend well beyond endourologic stone surgery:

  • Retrograde pyelography and stent placement at the time of urogyn / pelvic surgery — sacrocolpopexy, complex hysterectomy, deep-endometriosis resection, oncologic pelvic clearance — for intraoperative ureteral identification and protection.
  • Iatrogenic ureteral injury management — primary tool for retrograde wire passage when injury is identified intraoperatively or postoperatively, before DJ stent placement or surgical repair.
  • Ureteral reimplant and Boari-flap planning — preoperative RUG with hydrophilic wire and open-ended catheter to define stricture length / location.
  • Difficult urethral catheterization — the Freid–Smith Glidewire technique (1996) uses a hydrophilic wire passed per urethra in filiform-like fashion, exchanged for a standard wire, then coaxial dilation — successful in 19 / 20 attempts where filiform-and-follower had failed.[1][9] See Balloon Dilator and S-Shaped Coaxial Dilators.
  • Bedside flexible cystoscopy with guidewire-assisted catheter placement — the canonical alternative to filiform-and-follower for failed catheterization.
  • PCNL tract dilation (when reconstructive surgery follows stone or congenital UPJ disease) — Amplatz Super Stiff supports dilator and Amplatz sheath passage.
  • Antegrade nephroureteral access through a nephrostomy tube for refractory retrograde failure — same wire categories, antegrade route.

Wire-Selection Cheat Sheet​

ScenarioRecommended wireWhy
Routine ureteral accessStandard PTFE or hydrophilicFlexible tip navigates normal ureter safely
Difficult or impacted stricture / stoneHydrophilic (Glidewire)Lowest force, highest bypass success, highest perforation margin
Iatrogenic ureteral injuryHydrophilic (Glidewire)Atraumatic across edema / kink
UAS / Amplatz sheath placementAmplatz Super StiffMaximum axial rigidity
PCNL tract dilationAmplatz Super StiffSupports dilator and Amplatz sheath
Tortuous ureterHydrophilicLowest friction / pull force / safest tip
Stent placement (routine)Standard or hybridModerate stiffness sufficient
Difficult access + planned instrument passageHybrid (Sensor / U-Nite)Hydrophilic tip + stiffer working shaft
Failed urethral catheterizationHydrophilic (Glidewire)Freid–Smith technique[9]

The Safety-Wire Concept — Evolving​

Historically a safety wire was kept alongside the ureteroscope to preserve access if perforation occurred. Modern evidence increasingly challenges routine safety-wire use:

  • Ulvik 2013 (n = 500 each hospital) — no difference in scope passage, stone access, or stent placement; safety wire actually higher post-endoscopic stenosis (3.4% vs 1.2%, p = 0.039) and lower stone-free rate (77.1% vs 85.9%, p = 0.001).[10]
  • Eandi 2008 — safety wire adds 12 g (semirigid) / 20 g (flexible) to ureteroscope advance force ex vivo; clinical series of 361 ureteroscopies without safety wire reported no related complications.[11]
  • Dickstein 2010 — 270 uncomplicated flexible URS without safety wire — no loss of access, perforation, avulsion, or PCN.[12] 35 complicated cases still needed one.
  • Breda 2016 — Flexor Parallel Rapid Release UAS with guidewire disengagement allows a single wire to serve both roles; 94% successful insertion.[13]
  • Dutta 2016 "Death of the safety guidewire" — frames the routine safety wire as obsolete for uncomplicated URS; retained for complicated cases (difficult access, large stone burden, concomitant ureteral pathology).[14]

In reconstructive-urology practice the safety-wire question is somewhat different — when working in a previously instrumented, irradiated, or post-fistula ureter, the threshold for retaining a safety wire is lower because the cost of lost access can mean conversion to open repair.

Ureteral Perforation Force​

  • Human ureter perforation force: 0.79 ± 0.25 lb (significantly less than porcine 1.30 ± 0.25 lb, p = 0.013) — the bench-to-clinic translation reminder when using porcine training data.[15]
  • Glidewire required the greatest perforation force among hydrophilic wires — highest safety margin.[1][6]
  • Safety wire alongside a UAS increases UAS insertion force (mean 1.79 vs 0.67 kg, p = 0.0003; max 2.29 vs 1.00 kg, p = 0.0007) without significantly increasing ureteral-laceration rate ex vivo.[16]

Practical Considerations​

  • Hydrophilic wires must be kept wet — they become sticky when dry; have saline at hand during exchange.
  • Stiff wires can straighten a tortuous ureter and cause mucosal injury — exchange to a stiff wire only after the access wire is safely in the renal pelvis.
  • Wire exchange technique — gain access with a flexible hydrophilic wire, then exchange over an open-ended ureteral catheter for an Amplatz Super Stiff before advancing larger instruments.[1][17]
  • No standardized stiffness classification across manufacturers — wire labels are not directly comparable; choose by your institutional experience.[8]

Limitations​

  • No universal stiffness standard — manufacturer labels ("stiff" / "extra stiff") not quantitatively comparable.[8]
  • Hydrophilic-coating dry-out — recoats only with saline, can fail in long cases.
  • Tip behavior on bench vs in vivo can differ — porcine perforation data overestimate margin vs human.[15]

See also: Open-Ended Ureteral Catheters, Double-J Stent, Nephrostomy Tube, Balloon Dilator, S-Shaped Coaxial Dilators, Filiforms & Followers.

References​

1. Clayman M, Uribe CA, Eichel L, et al. "Comparison of guide wires in urology. Which, when and why?" J Urol. 2004;171(6 Pt 1):2146–50. doi:10.1097/01.ju.0000124486.78866.a5

2. Liguori G, Antoniolli F, Trombetta C, et al. "Comparative experimental evaluation of guidewire use in urology." Urology. 2008;72(2):286–9. doi:10.1016/j.urology.2007.12.098

3. Gotman I. "Characteristics of metals used in implants." J Endourol. 1997;11(6):383–9. doi:10.1089/end.1997.11.383

4. Balakrishnan N, Uvelius B, Zaszczurynski P, Lin DL, Damaser MS. "Biocompatibility of nitinol and stainless steel in the bladder: an experimental study." J Urol. 2005;173(2):647–50. doi:10.1097/01.ju.0000143197.93944.14

5. Amasyali AS, Groegler J, Hajiha M, et al. "What guidewire is the best for bypassing an impacted ureteral stone?" J Endourol. 2020;34(5):629–36. doi:10.1089/end.2020.0058

6. Torricelli FC, De S, Sarkissian C, Monga M. "Hydrophilic guidewires: evaluation and comparison of their properties and safety." Urology. 2013;82(5):1182–6. doi:10.1016/j.urology.2013.07.024

7. Sarkissian C, Korman E, Hendlin K, Monga M. "Systematic evaluation of hybrid guidewires: shaft stiffness, lubricity, and tip configuration." Urology. 2012;79(3):513–7. doi:10.1016/j.urology.2011.10.017

8. Kolvatzis M, Sierra A, Corrales M, Traxer O. "Stiff guidewires in endourology: what is stiffness?" J Endourol. 2022;36(11):1475–82. doi:10.1089/end.2022.0165

9. Freid RM, Smith AD. "The Glidewire technique for overcoming urethral obstruction." J Urol. 1996;156(1):164–5.

10. Ulvik Ø, Rennesund K, Gjengstø P, Wentzel-Larsen T, Ulvik NM. "Ureteroscopy with and without safety guide wire: should the safety wire still be mandatory?" J Endourol. 2013;27(10):1197–202. doi:10.1089/end.2013.0248

11. Eandi JA, Hu B, Low RK. "Evaluation of the impact and need for use of a safety guidewire during ureteroscopy." J Endourol. 2008;22(8):1653–8. doi:10.1089/end.2008.0071

12. Dickstein RJ, Kreshover JE, Babayan RK, Wang DS. "Is a safety wire necessary during routine flexible ureteroscopy?" J Endourol. 2010;24(10):1589–92. doi:10.1089/end.2010.0145

13. Breda A, Emiliani E, Millán F, et al. "The new concept of ureteral access sheath with guidewire disengagement: one wire does it all." World J Urol. 2016;34(4):603–6. doi:10.1007/s00345-015-1638-9

14. Dutta R, Vyas A, Landman J, Clayman RV. "Death of the safety guidewire." J Endourol. 2016;30(9):941–4. doi:10.1089/end.2016.0314

15. Pedro RN, Hendlin K, Weiland D, et al. "In vitro evaluation of ureteral perforation forces." Urology. 2007;70(3):592–4. doi:10.1016/j.urology.2007.04.050

16. Graversen JA, Valderrama OM, Korets R, et al. "The effect of extralumenal safety wires on ureteral injury and insertion force of ureteral access sheaths: evaluation using an ex vivo porcine model." Urology. 2012;79(5):1011–4. doi:10.1016/j.urology.2011.11.002

17. Linder BJ, Occhino JA. "Cystoscopic ureteral stent placement: techniques and tips." Int Urogynecol J. 2019;30(1):163–5. doi:10.1007/s00192-018-3762-8